Abstract 17241: Conversion of Recurrent Arrhythmia by the Wearable Cardioverter-defibrillator
Background: Sudden cardiac arrest (SCA) due to ventricular tachycardia (VT) or fibrillation (VF) reportedly reoccurs after an initial successful defibrillation in 60% or more of patients (pts). First responder programs have been associated with 25-71% return of spontaneous circulation (ROSC) and 73% survival to hospital admission when pts require additional, more than one, defibrillation treatment shock. Although VT/VF SCA occurring in wearable cardioverter defibrillator (WCD) pts has a 98% first shock success and 94% survival, the incidence and outcomes of recurrent VT/VF after an initial, successful shock is unknown.
Methods: The ZOLL registry of WCD pts was used to identify 1,219 USA pts appropriately treated from Oct 2009 through Aug 2014. Pts were included if they met the following: Group A, 1 shock in response to a detection cycle triggered by a single VT/VF episode; Group B, 1 shock in response to the first of two consecutive detection cycles, and 1 or more appropriate shocks delivered in response to a second, recurring VT/VF episode.
Results: There were 1,145 pts successfully converted with the first shock to VT/VF. Of these, 846 (74%) did not have VT/VF recurrence (Group A), while 299 (26%) were defibrillated again for recurrent VT/VF (Group B), with a median time between treatments of 71 minutes. Demographic and clinical characteristics of Group A and Group B differed only in the frequency of implantable cardioverter defibrillator explant pts (p<.01), which was increased 2-fold in Group B. First shock efficacy among Group A was high with 97% conversion success and 92% acute survival observed. Among Group B pts the recurring VT/VF shock conversion (97%) and acute survival (92%) was not significantly different, and conversion success was independent of the elapsed time between episodes. Deaths in Group B were primarily associated with a shorter elapsed time (10 minutes or less) between new VT/VF episodes (Pearson’s correlation 0.99).
Conclusions: A smaller fraction of WCD pts (26%) experience recurrent VT/VF than reported during first responder resuscitation. Conversion success of recurrent VT/VF among WCD pts was 97% and independent of the elapsed time between VT/VF episodes. SCA survival regardless of VT/VF recurrence was high, 92%.
Author Disclosures: S. Ringquist: Employment; Significant; ZOLL. N.R. Bianco: Employment; Significant; ZOLL. S.J. Szymkiewicz: Employment; Significant; ZOLL.
- © 2015 by American Heart Association, Inc.